Motor and gear parts are combined with a common shaft, which may all be retained within a housing as an integral gearmotor. A method of manufacturing such a gearmotor and motors in general establishes a desired air gap between the rotor and stator of a motor.
In power drive applications, it is conventional for motive power devices, such as motors, and gear systems to be separately manufactured, paired in accordance with their characteristics and then installed. Such an approach requires that a separate motor and gear system be coupled together. In real world applications, any point of coupling always presents some problems. Such problems may take the form of a slight introduction of inefficiency in operation such as a minor loss of transferred power, or, in a worst case, an absolute failure of the coupling such that no power is transferred.
The seriousness of minor power losses depends on the particular power drive application. However, some applications, such as conveyor belt drive systems associated with food preparation operations, are particularly critical with respect to certain other failure aspects of conventional motor/gear system couplings. For example, gears are often immersed in a lubricating oil. Coupling of such gears to a motor presents a potential oil leakage problem. Moreover, such leakage problems are aggravated by the fact that a coupling between a motor and its gear system is usually a high speed linkage. Leakage of such lubricating oil, even in small amounts, into a food preparation environment is not only highly undesirable, but might actually cause the manufacturer or food processor to stand in violation of applicable laws.
Aside from oil leakage problems, mechanical couplings between motors and gears are often difficult to decouple for required maintenance, such as repairing or replacing the motor or gears. Lengthy maintenance times generate high labor costs. High materials cost are caused as well if either a "healthy" motor or gear system is needlessly damaged while the other is receiving maintenance.
These and many other problems associated with conventional coupled gear and motor drives are addressed and solved by this invention. For example, the coupling problem is totally obviated by providing a gearmotor which includes a first shaft axial with the motor and extending outwardly therefrom; a rotor assembly, within the motor, disposed about and attached to the first shaft; a first gear secured to the extended portion of the first shaft; a plurality of bearing assemblies for rotatably supporting the first shaft at each of its ends and along its length between the motor and the first gear; an output shaft; and a second gear operatively associated with the first gear and output shaft so as to drive the output shaft. The resulting integral gearmotor with this extended shaft feature can thus have no oil leakage, vibration or misalignment problems at any mutual gear/motor coupling since no such conventional "coupling" exists.
Further disclosed as an aspect of this invention are certain housing features usable in combination with the present gearmotor. Improved manufacturing of such a gearmotor and motors in general is also achieved in accordance with additional features herein specifically disclosed below. For example, a shim technique may be practiced to accurately form a desired air gap between the stator and rotor of a motor. This shim method also insures a high degree of concentricity for the stator and rotor, which is well known to be an important aspect of establishing a high efficiency rating for a motor.
In summary, the shim method in accordance with one embodiment of this invention includes: resting a motor stator element on a support frame; rotatably fixing the motor rotor element to the frame and within the stator; placing shim means into an air gap formed between the stator and rotor so as to establish a desired and concentric air gap; securing the stator element to the support frame; and removing the shim means. The resulting motor has a predetermined air gap and desired concentricity without any need for or expense of carefully machined bores and bearings.